Evidence for heterogeneity in the 160/165×103mr glycoprotein components of desmosomes

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Abstract
We have prepared both monoclonal and polyclonal antibody preparations directed against the 160/165 ×103Mr glycoproteins (desmogleins) of bovine tongue epithelial desmosomes. The polyclonal antibody preparation recognizes desmosomes in a number of mouse tissues, e.g. mouse skin, heart, bladder and trachea, as determined by immunofluorescence microscopy. Furthermore, the polyclonal antibodies recognize poly-peptide(s), present in the high salt, Triton-insoluble residues (‘cytoskeleton preparations’) of mouse skin, heart, bladder and trachea, which comigrate with the 160/165×103Mr glycoproteins of bovine tongue epithelial desmosomes as determined by ‘Western’ immunoblotting. Conversely, the monoclonal 160/165 × 103Mr antibody preparation recognizes desmosomes of stratified squamous epithelial tissues but not desmosomes in other tissue types. Moreover, whereas the monoclonal antibodies recognize 160/165 × 103Mr polypeptides in mouse skin cell cytoskeletons they show no immunoreactivity with the cytoskeleton preparations of mouse bladder, trachea and heart following immunoblotting. These results suggest therefore that although there are conserved epitopes of the 160/165 × 103Mr glycoproteins there are also epitopes of these molecules which vary from tissue to tissue. Double label immunofluorescence observations of cryostat sections of mouse skin using the monoclonal antibodies and antibodies directed against desmoplakin, a plaque component of desmosomes, reveal that the monoclonal antibodies do not recognize certain desmosomes in basal cells which are recognized by desmoplakin antibodies. Indeed, double label observations of cryostat sections of mouse skin using the monoclonal antibodies and human autoantibodies which react with hemidesmosomal components suggest that the monoclonal antibodies stain desmosomes located along the apical surfaces of basal cells but fail to recognize desmosomes along the lateral surfaces of these same cells. The latter desmosomes, however, are recognized by the polyclonal 160/165 × 103Mr antibody preparation. We discuss the possibility that the inherent polarity of basal epithelial cells is manifested in modifications of the 160/165×103Mr glycoproteins in desmosomes located along different surfaces of basal cells.